Factsheet of the month: July – Maize Lethal Necrosis Disease

20137804184-page-0On Friday, the International Plant Protection Convention (IPPC) released an official pest report, submitted by KEPHIS, for the presence of Maize lethal necrosis disease (MLND) in Kenya. This disease is caused by a co-infection of Maize Chlorotic Mottle Virus and another cereal potyvirus, such as Sugarcane Mosaic Virus, Wheat Streak Mosaic Virus or Maize Dwarf Mosaic Virus. This co-infection causes more severe symptoms that either of the viruses causes alone. Symptoms include mottling, stunting, necrosis and malformed ears.

MLND can devastate maize crops, impacting farmers’ incomes and the food security of the area. To find out how to recognise and control MLND, read the Plantwise Factsheet for Farmers created by employees from the Ministry of Agriculture and CABI.

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New strategy required for delaying insect resistance to Bt crops

Kenyan farmer Mary Ngare in her maize field damaged by stem borers © CIMMYT (CC BY-NC-SA)

Kenyan farmer Mary Ngare in her maize field damaged by stem borers © CIMMYT (CC BY-NC-SA)

Transgenic Bt crops have been grown around the world since the 1990s and have contributed to increased yields by controlling agricultural pests. Due to the importance of this technology, there has been continuous study into the development of resistance to Bt crops and how best to avoid this happening. A recent investigation into the rapid spread of Bt resistance in South Africa has revealed one of the more surprising discoveries to date, that the maize stalk borer (Busseola fusca) has evolved Bt maize resistance inherited as a dominant trait for the first time. This has significant impacts on the management of Bt crops, as current methods for sustaining susceptibility rely on the recessive inheritance of Bt resistance.

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Update: Plant Health News (31 Jul 13)

Phythophthora sojae causes root and stem rot of soybean © Daren Mueller, Iowa State University (CC BY-NC)

Phythophthora sojae causes root and stem rot of soybean © Daren Mueller, Iowa State University (CC BY-NC)

Here’s a taste of some of the latest stories about plant health, including reports of citrus greening (huanglongbing) in Paraguay, the discovery of genes resistant to Phytophthora sojae in soybeans and a computer model that gives early warning signs of crop failure.

Click on the link to read more of the latest plant health news!
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Corn rootworm resistance to crop rotation explained

Adult western corn rootworms on maize leaves

Adult western corn rootworms on maize leaves © Stefan Töpfer, CABI

Crop rotation is often recommended as an effective control method against agricultural pests, including corn rootworms. Rotation works by removing the host on which the pest feeds and reproduces, and planting a crop which they are unable to live on. This reduces the number of pests that survive to the next season. Crop rotation is a common approach used to control the corn rootworm (Diabrotica virgifera virgifera) which, as you can probably guess, is a major pest of corn (Zea mays). These rootworms lay their eggs in corn fields, so that when the eggs hatch, the larvae can feed on the corn roots in the field. Rotating corn with soybean (Glycine max) means the farm remains productive in all seasons, while the soybean’s natural antiherbivory defences keep corn rootworm numbers low. This method saves the farmer money that could otherwise be lost through yield losses, the purchase of insecticides or the purchase of corn hybrids toxic to rootworms, which in total costs growers in the USA at least $1 billion per year.

In the past few years, however, growers practising crop rotation have seen an increase in the number of corn rootworms resistant to the rotation method. Scientists studying the corn rootworm have previously drawn a blank when trying to discover why some rootworms were more resistant. It’s only when they stopped looking at the organism itself that they found an explanation.

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Maize Lethal Necrosis Disease Spreads To Uganda

Maize plants showing Maize Lethal Necrosis disease © CIMMYT via Flickr (License CC-BY-NC-SA 2.0)

Maize plants showing Maize Lethal Necrosis disease © CIMMYT via Flickr (License CC-BY-NC-SA 2.0)

Maize Lethal Necrosis disease, which was first reported in Kenya and Tanzania, has now spread to Uganda, raising concerns for food security in the country. The Ministry of Agriculture has warned that Maize Lethal Necrosis has been reported in districts in eastern Uganda, including Busia and Tororo.

A spokesman for the Agriculture Research Organisation, Robert Anguzo, has said that Ugandan scientists are working in collaboration with the International Maize and Wheat Improvement Centre (CIMMYT) to find management solutions to the disease.

More information about the pests and viruses associated with Maize Lethal Necrosis and the management of the disease can be found on the Plantwise Knowledge Bank

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How The Gates Foundation and Carlos Slim are Supporting Innovation and Crop Improvement For Farmers

Carlos Slim, Bill Gates and Mexican Dignitaries visit CIMMYT to inaugurate the new Bioscience facilities © Eruviel Avila (CC-BY-NC-SA 2.0)

Carlos Slim, Bill Gates and Mexican Dignitaries visit CIMMYT to inaugurate the new Bioscience facilities © Eruviel Avila (CC-BY-NC-SA 2.0)

The Bill & Melinda Gates Foundation and Fundación Carlos Slim have announced a partnership in support of efforts by the Centro Internacional de Mejoramiento de Maíz y Trigo (International Maize and Wheat Improvement Center CIMMYT) in Mexico to develop and disseminate higher-yielding, more resilient wheat and maize varieties. Read more of this post

CABI scientists help to uncover new occurrences of plant diseases

Tertiary vein chlorosis of Cassava Brown Streak Disease, just one of the diseases CABI scientists have worked on in 2012 ©  IITA  (CC By-NC licence)

Tertiary vein chlorosis of Cassava brown streak disease, just one of the diseases CABI scientists worked on in 2012 © IITA (CC BY-NC licence)

In 2012, CABI scientists continued to contribute to the discovery of new occurrences of plant pests and diseases, via the Plantwise diagnostic service. CABI’s Plantwise initiative offers a free service for eligible clients in developing countries, providing disease identification support to plant clinics. Every year, the DFID-funded service receives more than 500 samples from 80 different countries. CABI and Food and Environment Research Agency (FERA) scientists then diagnose the problem and report any new occurrences of pathogens they find. The following published reports contain examples of new occurrences discovered in 2012.

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